纳米Cu/Ti-Si3N4陶瓷基板的界面作用及抗热疲劳机理研究

Thermal stress fatigue failure caused by mismatch in the coefficients of thermal expansion (CTE) between the metal layer and ceramic plate during a high and low temperature cycle is considered as the big issue of high-power ceramic substrates. This project focus on the formation of nano Cu/Ti-Si3N4 ceramic substrates by SPS hot pressing sintering to tackle the problems in thermal stress fatigue. The effects of processing parameters on the microstructure of metallized Layer and interface of the nano Cu/Ti-Si3N4 ceramic substrates are investigated, thus, the formation mechanism of nano-metallized layer and interfacial interaction mechanism between Cu and Ti-Si3N4 under the activation of thermal pressure and plasma will be explored. The change regulation of microstructure of metalled layer and the interfacial evolution between Cu and Ti-Si3N4 during a high and low temperature cycle are investigated, thus, the thermal fatigue damage mechanism of nano Cu/Ti-Si3N4 ceramic substrates as well as the plastic deformation mechanism for resistting thermal fatigue by nano-metallized Cu will be explore, finally, the interaction mechanism of resistting thermal fatigue by nano Cu/Ti-Si3N4 ceramic substrates will be revealed. The study of this project not only provides crucial experimental and theoretical foundation for the fabrication of high-power ceramic substrates, but also is of great significance for the knowledge enrichment of the interfacial interaction mechanism and thermal fatigue damage mechanism.

针对大功率、超大功率陶瓷基板在高低温冷热循环作用下陶瓷金属热膨胀系数失配引起的热应力疲劳（热疲劳）难题，本项目采用SPS热压烧结技术，制备纳米Cu/Ti-Si3N4陶瓷基板，研究烧结工艺对陶瓷基板金属化层及界面微观结构的影响规律，探索热压温度场和等离子活化作用下纳米Cu金属化层的成形机制及Cu与Ti-Si3N4陶瓷间的界面作用机制；研究高低温循环过程中陶瓷基板金属化层微观结构的变化规律，界面微观结构的演化规律，探索纳米Cu/Ti-Si3N4陶瓷基板的热疲劳损伤机理及纳米Cu抵抗热疲劳的塑性变形机制，揭示纳米Cu/Ti-Si3N4陶瓷基板抗热疲劳的作用机理。本项目的研究不仅为大功率陶瓷基板的制造提供重要的理论依据和数据基础，而且对丰富大功率陶瓷基板界面反应机制和热疲劳损伤的理论也具有重要得意义。

针对大功率、超大功率陶瓷基板在高低温冷热循环作用下陶瓷金属热膨胀系数失配引起的热应力疲劳（热疲劳）难题，本项目采用SPS技术，制备了纳米Cu-Si3N4陶瓷基板，研究了烧结工艺对陶瓷基板金属化层及界面微观结构的影响规律，探索了热压温度场和等离子活化作用下纳米Cu金属化层的成形机制及Cu与Ti-Si3N4陶瓷间的界面作用机制。在温度和压力一定时，随着保温时间的逐渐延长，纳米铜粉微观结构的演变经过粉末的活化、烧结颈的形成和烧结颈的生长三个阶段实现纳米铜粉的快速致密化过程。通过添加Ti过渡层成功制备了纳米Cu-Si3N4陶瓷基板，SPS烧结过程中Ti过渡层首先演变成Ti2O层，然后随着保温时间增加而形成在双层结构：一层（Ti2O）结合到Si3N4陶瓷，而另一层(Ti4Cu2O(Ti3Cu3O),Cu)结合到纳米Cu金属层，此结构的形成保障了界面结合强度。另外，我们推测界面反应机制为（i）Cu2O的分解和Ti固溶体（Ti[O]）的形成；（ii）Cu层中Ti-Cu-O化合物（Ti4Cu2O,Ti3Cu3O）的形成;（iii）Ti2O层中Ti-Cu-O合物(Ti4Cu2O,Ti3Cu3O)的形成。这三个反应与O、Ti和Cu原子在等离子体活化下的扩散密切相关。界面处形成的Ti3Cu3O化合物还可能起到缓解界面热应力的作用。本项目还研究了高低温循环过程中陶瓷基板金属化层微观结构的变化规律，界面微观结构的演化规律。1）随着冷热循环周次的增加，样品的氧化程度增加，表面粗糙度增加。2）随着热疲劳实验过程的延长界面处逐渐会发生明显的元素扩散现象，进而会促进界面反应的进行。经过100次热循环的疲劳实验，界面微观结构变化不大，在进行热循环的过程中Ti反应层保持稳定；当热循环到400周次时，界面反应层出现较大变化，直到500周次导致界面处Ti2Cu3、Cu2O等化合物的出现，同时也在过渡层发现纳米孪晶铜。纳米孪晶的形成可能起到了明显缓解界面热应力的作用，有利用提高陶瓷基板的热疲劳抗力。本项目的研究对丰富大功率陶瓷基板界面反应机制和热疲劳损伤理论具有重要得意义。